First measurements of low-energy cosmic rays on the surface of the lunar farside from Chang’E-4 mission

The intensity of low-energy cosmic rays on the lunar farside is consistent with that observed in the near-earth space.

Measurement of Energy Spectrum and Elemental Composition of PeV Cosmic Rays: Open Problems and Prospects

Cosmic rays represent one of the most important energy transformation processes of the universe. They bring information about the surrounding universe, our galaxy, and very probably also the extragalactic space, at least at the highest observed energies. More than one century after their discovery, we have no definitive models yet about the origin, acceleration and propagation processes of the radiation. The main reason is that there are still significant discrepancies among the results obtained by different experiments located at ground level, probably due to unknown systematic uncertainties affecting the measurements. In this document, we will focus on the detection of galactic cosmic rays from ground with air shower arrays up to 1018 eV. The aim of this paper is to discuss the conflicting results in the 1015 eV energy range and the perspectives to clarify the origin of the so-called `knee’ in the all-particle energy spectrum, crucial to give a solid basis for models up to the end of the cosmic ray spectrum. We will provide elements useful to understand the basic techniques used in reconstructing primary particle characteristics (energy, mass, and arrival direction) from the ground, and to show why indirect measurements are difficult and results are still conflicting.

EAS Observation Conditions in the SPHERE-2 Balloon Experiment

The SPHERE project studies primary cosmic rays by detection of the Cherenkov light of extensive air showers reflected from the snow covered surface of the earth. Measurements with the aerial-based detector SPHERE-2 were performed in 2011–2013. The detector was lifted by a balloon to altitudes of up to 900 m above the snow covered surface of Lake Baikal, Russia. The results of the experiment are summarized now in a series of papers that opens with this article. An overview of the SPHERE-2 detector telemetry monitoring systems is presented along with the analysis of the measurements conditions including atmosphere profile. The analysis of the detector state and environment atmosphere conditions monitoring provided various cross-checks of detector calibration, positioning, and performance.

Method of Separating Cosmic-Ray Positrons from Electrons in the DAMPE Experiment

A method of identifying positron/electron species from the cosmic rays was studied in the DAMPE experiment. As there is no onboard magnet on the satellite, the different features imposed by the geomagnetic field on these two species were exploited for the particle identification. Application of this method to the simulation of on-orbit electrons/positrons/protons and the real flight data proves that separately measuring the CR positrons/electrons with DAMPE is feasible, though limited by the field of view for the present observation data. Further analysis on the positron flux with this method can be expected in the future.

Application of ASAS method to PAMELA calorimeter

In this paper, we propose a method that makes it possible to to improve energy reconstruction for data obtained via thin heterogeneous calorimeters for direct measurements of cosmic rays with energies of TeV and higher. Despite the large number of modern experimental complexes, the primary energy of cosmic nuclei with energies above 1 TeV is determined with large errors associated with fluctuations in the development of the cascade. For heterogeneous calorimeters, transient effects give an additional negative effect. In this paper we analyze the main causes of fluctuations and discuss a method for reducing the effect of fluctuations on the results of primary energy reconstruction. The method of accumulation of signal along the spectrum (ASAS) is used to reduce fluctuations associated with transient effects. The method was tested using the heterogeneous calorimeter of the PAMELA collaboration. It is shown that the proposed approach makes it possible to correctly determine the energy of slowly developing showers, the maxima of which are not measured.

Hadron interactions for arbitrary energies and species, with applications to cosmic rays

The Pythia event generator is used in several contexts to study hadron and lepton interactions, notably $$\mathrm{p}\mathrm{p}$$ p p and $$\mathrm{p}{\bar{\mathrm{p}}}$$ p p ¯ collisions. In this article we extend the hadronic modelling to encompass the collision of a wide range of hadrons h with either a proton or a neutron, or with a simplified model of nuclear matter. To this end we model $$h\mathrm{p}$$ h p total and partial cross sections as a function of energy, and introduce new parton distribution functions for a wide range of hadrons, as required for a proper modelling of multiparton interactions. The potential usefulness of the framework is illustrated by a simple study of the evolution of cosmic rays in the atmosphere, and by an even simpler one of shower evolution in a solid detector material. The new code will be made available for future applications.

Observational Constraints on the Maximum Energies of Accelerated Particles in Supernova Remnants: Low Maximum Energies and a Large Variety

Supernova remnants (SNRs) are thought to be the most promising sources of Galactic cosmic rays. One of the principal questions is whether they are accelerating particles up to the maximum energy of Galactic cosmic rays (∼PeV). In this work, a systematic study of gamma-ray-emitting SNRs is conducted as an advanced study of Suzuki et al. Our purpose is to newly measure the evolution of maximum particle energies with increased statistics and better age estimates. We model their gamma-ray spectra to constrain the particle-acceleration parameters. Two candidates of the maximum energy of freshly accelerated particles, the gamma-ray cutoff and break energies, are found to be well below PeV. We also test a spectral model that includes both the freshly accelerated and escaping particles to estimate the maximum energies more reliably, but no tighter constraints are obtained with current statistics. The average time dependences of the cutoff energy (∝t −0.81±0.24) and break energy (∝t −0.77±0.23) cannot be explained with the simplest acceleration condition (Bohm limit) and require shock–ISM (interstellar medium) interaction. The average maximum energy during lifetime is found to be ≲20 TeV ( t M / 1 kyr ) − 0.8 with t M being the age at the maximum, which reaches PeV if t M ≲ 10 yr. The maximum energies during lifetime are suggested to have a variety of 1.1–1.8 dex from object to object. Although we cannot isolate the cause of this variety, this work provides an important clue to understanding the microphysics of particle acceleration in SNRs.

Time course of semidiurnal variations in the intensity of cosmic rays according to the data of ground-based detectors for 1971-2021.

Аннотация. Регистрируемые наземными детекторами галактические космические лучи (КЛ) по пути своего распространения подвергаются воздействию основного воздействующего фактора – солнечного ветра, заполняющего всю гелиосферу. Модуляция космических лучей гелиосферой приводит к образованию их анизотропного пространственно-углового распределения в межпланетном пространстве. В данных наземных детекторов КЛ такая анизотропия проявляет себя вследствие вращения Земли вокруг своей оси в виде периодических суточных колебаний регистрируемой интенсивности. Параметры таких колебаний определяются состоянием солнечной активности (СА) и соответствующими изменениями крупномасштабной структуры. Как правило, амплитуда подобных колебаний мала и составляет лишь сотые доли от общего потока КЛ. Однако анизотропия КЛ служит важным источником информации о свойствах и структуре всей гелиосферы. Существующая на сегодня картина модуляции КЛ в гелиосфере предполагает существование их избытка с направлений поперек силовых линий межпланетного магнитного поля (ММП). Экспериментальные данные подтверждают такую картину, и в среднем максимум колебаний наблюдается как раз в 3 и 15 ч по местному времени. Учитывая, что направление силовых линий поля сохраняется почти неизменным, справедливо ожидать, что указанное выше время максимума должно оставаться также неизменным. Однако длительные наблюдения показали, что в зависимости от уровня СА время максимума может существенно смещаться на раннее время. Данная работа представляет собой попытку объяснения наблюдаемых амплитудно-фазовых колебаний полусуточных вариаций интенсивности КЛ. На основе актуальных представлений о взаимодействии КЛ с атмосферой Земли и геомагнитным полем проведены расчеты ожидаемых полусуточных вариаций интенсивности КЛ, регистрируемых мировыми сетями мюонных детекторов и нейтронных мониторов. Сопоставление расчетных и наблюдательных данных показало, что наблюдаемое смещение возможно объяснить динамикой энергетического спектра полусуточных вариаций КЛ. Полученный результат подтверждает и дополняет полученные ранее другими авторами результаты, а также ее можно рассматривать как указание для дальнейшего развития теории гелиосферной модуляции КЛ.